DELOREAN WORKSHOP MANUAL - Free

D:04:14 Fuel Emission and Exhaust System
ELECTRICAL CIRCUIT FUNCTION
The Lambda relay (2) receives power from the
RPM relay and is energised only when the engine is
rotating. When the relay is energised, the contacts
close and voltage from fuse No. 7 is applied to the
frequency valve (3) and the ECU module (1).
The oxygen sensor (4) generates a signal voltage
(approximately 500 mv) which is carried by a
screened cable to the module. The signal voltage
will vary depending on the oxygen content in the
exhaust gas. The less oxygen content in the
exhaust (rich condition), the greater the signal
voltage produced by the sensor.
During operation, the ECU module will analyse the
oxygen sensor signal and send a pulse cycle signal
to the frequency valve. This signal will allow a
pulsating current flow to the valve which will turn it
on and off as required. The pulse cycle can be
measured by connecting a dwell meter to the
diagnostic plug which is connected to terminal No.
17 of the ECU module.
The full-throttle enrichment switch (5) sends a
ground signal to the ECU module when the throttle
is in the wide-open position. The thermal switch
(6) also sends a ground signal to the ECU module
when the coolant temperature is below 15°C
(59°F). These two switches override the oxygen
sensor input to the ECU module, allowing a fixed
pulse cycle to be sent to the frequency valve. (Fig.
33)
SYSTEM REPAIR NOTES
All of the Lambda system parts, with the exception
of the throttle microswitch, are sealed units and
cannot be adjusted or repaired. Tampering with a
sealed unit will automatically void the warranty.
1. The Lambda ECU module is located in the
module compartment behind the driver's
seat. It is in the forward section of the
compartment and is silver in colour.
2. When replacing the oxygen sensor, it is
necessary to use an antiseize compound on
the sensor threads. Do not allow any of the
compound to get on the tube projecting from
the sensor. Do not attempt to disconnect the
wire lead directly at the sensor.
3. If it is necessary to supply power to the
Lambda system when the engine is not
running, by-pass the RPM relay by removing
the relay and connecting a jumper wire
between terminals No. 87b and No. 30 in the
connector. The RPM relay is located in the
relay compartment behind the passenger
seat. (See "Electrical System and
Instruments" Section M).
4. When checking the pulse ratio, a fluctuating
dwell reading when the sensor is connected
indicates that the system is operating.
Readings above or below specifications could
be caused by a rich or lean CO adjustment.
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